One issue associated with biosynthesis of isoprenoids is the availability of pathway precursors and competition with other central metabolic pathways. The conservation of metabolic materials (carbon) and energy is a crucial aspect of producing bioenergy in an economically competitive manner when compared to petroleum derived fuels.
As there was no known direct metabolic route from xylose to DXP, it was hoped that a synthetic pathway could be generated by identifying mutant enzymes that could catalyze novel metabolic steps. To this end, a strain of E. coli that cannot generate DXP from the normal precursors, pyruvate and glyceraldehyde-3-phosphate (G3P) is constructed, and this strain is used to select for mutants that could convert xylose to DXP.
Currently, DXP is produced by the condensation of pyruvate and glyceraldehyde-3-phosphate (G3P). This condensation results in the loss of CO2 and is not an efficient method for the production of DXP. In addition, pyruvate and G3P are required for many metabolic pathways in the cell, and normally only a small fraction of these precursors is directed to DXP biosynthesis.